linux-kernel - Re: [PATCH] driver-core : get_device before create/remove sysfs files

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Date:	Thu, 31 Jan 2008 09:17:18 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Cornelia Huck" <cornelia.huck@...ibm.com>
Cc:	gregkh@...e.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] driver-core : get_device before create/remove sysfs files

On Jan 30, 2008 6:32 PM, Cornelia Huck <cornelia.huck@...ibm.com> wrote:
> On Wed, 30 Jan 2008 09:56:25 +0800,
> Dave Young <hidave.darkstar@...il.com> wrote:
>
> > get dev reference before create/remove sysfiles, errno fixes as well.
> >
> > Signed-off-by: Dave Young <hidave.darkstar@...il.com>
> >
> > ---
> > drivers/base/core.c |   12 ++++++++----
> > 1 file changed, 8 insertions(+), 4 deletions(-)
> >
> > diff -upr a/drivers/base/core.c b/drivers/base/core.c
> > --- a/drivers/base/core.c     2008-01-30 09:49:56.000000000 +0800
> > +++ b/drivers/base/core.c     2008-01-30 09:49:56.000000000 +0800
> > @@ -414,7 +414,7 @@ struct kset *devices_kset;
> >   */
> >  int device_create_file(struct device *dev, struct device_attribute *attr)
> >  {
> > -     int error = 0;
> > +     int error = -ENODEV;
>
> Uhm... why?

In this function :
        if (get_device(dev)) {
                do create issue
        }
        return error

So IMO the initial error should be -ENODEV

>
> >       if (get_device(dev)) {
> >               error = sysfs_create_file(&dev->kobj, &attr->attr);
> >               put_device(dev);
> > @@ -442,9 +442,11 @@ void device_remove_file(struct device *d
> >   */
> >  int device_create_bin_file(struct device *dev, struct bin_attribute *attr)
> >  {
> > -     int error = -EINVAL;
> > -     if (dev)
> > +     int error = -ENODEV;
> > +     if (get_device(dev)) {
> >               error = sysfs_create_bin_file(&dev->kobj, attr);
> > +             put_device(dev);
> > +     }
>
> Why do we need to grab a reference here? If the calling site doesn't
> hold unto a reference already, something is seriously broken.

First, we should keep consistent with previous function "device_create_file";
Second, AFAIK this function mostly are called after something like device_add
and the dev reference are not hold.


>
> >       return error;
> >  }
> >  EXPORT_SYMBOL_GPL(device_create_bin_file);
> > @@ -456,8 +458,10 @@ EXPORT_SYMBOL_GPL(device_create_bin_file
> >   */
> >  void device_remove_bin_file(struct device *dev, struct bin_attribute *attr)
> >  {
> > -     if (dev)
> > +     if (get_device(dev)) {
> >               sysfs_remove_bin_file(&dev->kobj, attr);
> > +             put_device(dev);
> > +     }
>
> Dito.
>
>
> >  }
> >  EXPORT_SYMBOL_GPL(device_remove_bin_file);
>
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